On the weight topic, I would like to see those studies as well. While not plus sized now, I have been. I can say with conviction that when I was 200 lbs I was a better rider and easier on a horse than a lot of thin riders I've seen in my day.
My hubby is a stout 220 very muscular guy, his favorite ride at our place is a 14.2 bulldog cutting bred QH. That horse has zero trouble carrying my hubby and still moves like a cat on his feet.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.